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Changes in plasma levels of atrial natriuretic peptide (ANP) and albumin, and blood hematocrit (Hct) during treadmill exercise were studied in 6 healthy men before and after beta-adrenergic blockade. Plasma ANP levels increased during exercise and then gradually decreased. There was a concomitant increase in both Hct and plasma albumin concentrations. Prior administration of a long-acting propranolol, 160 mg daily for 3 consecutive days, markedly elevated plasma ANP levels before, during and after exercise. In addition, the mean basal Hct increased significantly and further rose during exercise after propranolol administration. When increments in plasma ANP concentrations during exercise in individual subjects were compared with those in Hct, there was a significant positive correlation between the two variables before and after propranolol administration. The results indicate a close relationship between the changes in plasma ANP and those in Hct during exercise at different ANP levels, and suggest that ANP may be at least one of the factors involved in the hemoconcentration associated with exercise.

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SUMMARYChanges in plasma levels of atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) were studied in 8 patients during a 30 min period of induced supraventricular tachycardia (SVT). The mean plasma ANP concentration increased immediately after the onset of SVT, peaked at 30 min and gradually returned to the control level. The mean plasma AVP concentration, on the other hand, was suppressed during SVT and rebounded above the control level in the post-SVT period. In 4 patients, SVT was associated with polyuric and natriuresis. The mean urine volume in these patients increased to 580% of the control and the mean urinary sodium excretion to 278% of the control, respectively. It was concluded that both a stimulation of ANP secretion and an inhibition of AVP release, elicited by an increase in atrial pressure, may be responsible for polyuria and natriuresis associated with SVT.

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